The present invention relates to cable television apparatus, and more particularly to a converter with remotely modifiable functionality provided by downloadable firmware.
As will be apparent from the following specification, the term "firmware" is used herein to describe functional operating software that is downloaded to a converter or other device and stored in nonvolatile memory. Until the downloaded "firmware" is changed, it resides in hardware (i.e., nonvolatile memory) just like conventional firmware. This concept of downloaded "firmware" is intended to emphasize that the present invention provides modifiable functionality in systems that heretofore could not be modified due to their reliance on permanent firmware.
Cable television converters are currently available that allow a cable system operator to remotely control subscriber service authorizations from a central "headend" site. These units, which are commonly referred to as "addressable converters", allow the cable system operator to control access to various premium services by sending a control signal from the headend to individual converters located at subscribers' homes. The authorization signals are carried on the cable television system, and enable individual subscribers to view programs that they pay an additional fee for. In operation, the control signals typically enable the converter to descramble the premium channels for viewing by the subscriber.
Other addressable systems currently available allow a limited set of operational parameters to be downloaded to a converter from the headend. Such operational parameters include, for example, information that maps displayed channels to tuned channels, time-out periods, barker channel(s), the converter output channel, the terminal configuration, and enable/disable functions for subscriber features such as remote hand-held control, parental control, favorite channel recall, volume control, and the like. The current state of the art is to download configuration information for a set of features that have been predetermined at the time of manufacture or installation of the cable television converter. An example of such a converter is the Model DPV7200 addressable converter manufactured by the Jerrold Division of General Instrument Corporation, Hatboro, Penna., U.S.A.
Other systems with downloadable data capabilities are also known. U.S. Pat. No. 4,054,911 to Fletcher, et al. relates to an information retrieval system capable of capturing packets or rows of video displayable data and/or control program instructions from data continuously transmitted in a common predetermined format. In the system disclosed in the patent, a user decides what information is to be retrieved, and takes action to cause a terminal to retrieve that information. Although a user can vary the function of the terminal by capturing different transmitted data, it is the user that determines what video displayable information is to be received, and how the terminal which receives this information is to process it. There is no disclosure or provision of means to enable a system operator to establish the functional operation of individual terminals on a multi-terminal network.
In commonly owned U.S. Pat. No. 4,712,239 to Frezza, et al. entitled "Security Arrangement for Downloadable Cable Television Converters", incorporated herein by reference, a downloadable converter is disclosed that prevents a false booter image from being downloaded. A false image could subject the system to various integrity problems, such as enabling an unauthorized user to view premium programs. In the patented system, a booter image is received on one channel and a checksum is computed therefrom. A valid checksum, extracted from tag data transmitted on a separate channel and associated with a scrambled program signal, is compared with the computed checksum. If the checksums do not match, a descrambler in the converter is precluded from descrambling the program signal. The system disclosed in this patent downloads all of the operating software to a cable television converter over a dedicated "booter channel", to which the converter is force tuned when first turned on. After the download is complete, the converter's data receiver is returned to the regular data channel, where it remains until the converte is turned off.
It would be advantageous to provide a method and system for downloading firmware to a remote terminal, such as a cable television converter, to allow modification of virtually any or all firmware functions of the terminal by the system operator. It would be further advantageous for such a method and system to enable the system operator to replace or modify options that were predetermined at the time of manufacture or installation of the terminal. By effecting terminal modifications automatically from a headend location, such a method and system would eliminate the need for a technician to travel to a subscriber's home to modify or physically replace a subscriber's terminal to effect such functional modifications.
The present invention provides such a method and system for remotely modifying the functionality of a cable television converter or other terminal.